Gas discharge lamp



` UNITED `s'liirlss PATENT ori-*ICE v Gasiil'szmanm 4 VvMilesPennybocker, Westport, Golm. Application my 29. i945, serial No.596,560Y

columnV gas discharge.

f invention includes 'certainelements and ieaturesof the lamp describedin my co-pending applicationV Serial #569,488,` illed December 23,

`comme (ci. 17e- 122) Positive column gas discharge lamps are y usuallyconstructed in the form of a relatively long Vand narrow cylinder ofglass, .quartz vor other suitable transparent or translucent material,pro- -videdwith suitable electrodes at b oth ends thereof. In one widelyused form, the internal surface'of the transparentenvelope is coatedwith as ultra violet. toanother portion ofthe spectrum better suited forgeneral illuminating purposes. Y

For most purposes, it is 'desired that the light from a l'lamp beemitted over anfarc of not exceeding 180 degrees. Accordingly, when acylindrically-shaped lamp is'employed, it is usually found necessary,or, at lleast lhighly desirable, to employ a reflector whichvwill renderavailable a portion of the light otherwisewastedby reason of the factthatit is emitted in an undesired direction. Y

One object 'of thisinventionjis to provide a novel form ofelongatedcylindrical lamp 'from which the externally available lightisemitted substantially wholly along onev longitudinal hall' of thecylinder. thus causing thelminous output of the lamp tov becompietely'available without which optical eillciency is increased bycausing the useful light to proceed directly from the surface of thephosphor which is acted 'upon by radiations coming from thepositive-column discharge, and'causing this light to pass` directly tothe exterior of the tube, without having to pass through any otherlayers of phosphonor through other semi-opaque material.

Other purposes and advantages of this invention will be apparent tothose skilled in the art from the following description of severalembodiments thereof. l.

Reference is now made to the drawings hereunto attached; where Fig. 1 isa perspective view of a. tube embodying one torm-oithis invention.

Fig. 2A is-a cross-sectional view of the tube oi l Fig. 1,

Fig. 2B is a cross-sectional view oia tube embodying another form ofIthis invention,

- tive form of this invention, using a divided reelements which havehitherto been formed as n metallic deposits', or the like, upon suchinternal wall, and lwhich reflector may also act as asupport forjailuorescent coating.. 4 l

A still further ,purpose of this invention is to provide a tubular lampin which the reilector can be manufactured independently of the tubevand` only,l insertedV therein when the tube is ready to be sealed. Thisdiscrete construction is 'well adapted .toA economical large scaleproduction, in

contrast to certain hitherto; vemployed methods' of constructingganinternal reiiector, in situ.`

ector strip.

Referring now to Figs. 1 and 2A, there is here.

shown an elongated tube I, of suitablegas-contlning material such asglass.` This material is chosen to be transparent to radiations havingsuch wave lengths as are to be utilized externally. For example, thetube may be constructed of ultra violet transmitting glass `or ofquartz, if the radiations lie in the ultra violet portion of thespectrum. Suitable electrodes of the cold cathode type, 2, are shown ateach end of the tube, but hot cathodesmay optionally be used. Extendinglongitudinally of the tube, but prefer.- ably terminating short of eachelectrode is a rejflecting strip 3. As shown in Fig. 2A, it is preferredthat thisstrip extend for approximately degrees around the internalperiphery of the tube. However. strips extending over a greater orlesser anglemay be employed without departure fromV this invention.Strip 3 may be" nesium and aluminium, but this invention is not qfthe'tube wall covered thereby. It is, however,

' possible to use a relatively less elastic material for the strip andto provide a coating of adhesive material between the strip and the tubewall, in order that the strip shall remain in the proper position, or itis possible to mount or fasten the strip in place by any other means.

In Fig. 2B there is shown Ia variant form 3" which the stripjustdescribed may assume. In this particular form, the apex of the V andextremities 'of the two arms of the V lconstitute three points ofcontact extending longitudinally along the tube wall. The tendency ofthe V to expand laterally may be used to hold the strip in place.

Evidently the surface of the reflecting strip should be chosen of anature to act as an eflicient reflector for the particular wave lengthswhich are to be emitted from the tube.

For confining the positive column discharge to the proper path thereof,it has been found desirable but not essential that the surface of aconducting reflecting strip which faces this path within the tube becovered with a layer of insulating material I. If the materialconstituting the surface of the reflector strip be metallic in nature,it may be desirable to place over it an outside layer of some materialwhich is relatively transparent or reflecting, but which is alsononconducting. Many white materials such as aluminum oxide, magnesiumoxide, or other metallic oxides, and the like, function both as asuitable rescent type, the visible light proceeds from Va material whichis usually non-conducting and only somewhat, transparent. Such phosphorsmay be used to cover the surface of the reflecting strip, in which casethe material functions not only as a light emitter, but also to acertain extent as a light reflector.

Another method of limiting undesired current flow through a conductivereflector is to form the reflector las a series of separate sections,electrically insulated from one another, so that the total voltage whichwould be required to supply the sum of the cathode-fall voltages as eachsuch section is greater than the maximum voltage of the correspondinglength o'f the positive discharge column, during norm-al starting orrunning. This arrangement will be hereinafter delscribed in greaterdetail.

an arc correspondingly less than 180 degrees.

4 This arrangement will in many cases eliminate the need for externalreflectors. By my use of a separate reflector strip bearing thephosphor.

Asuch type of lamp may be manufactured very simply. whereas it has beenfound very dimcult to coat the internal wall of a tube over only aportion of the periphery thereof.

In the particular form of construction just described, employing afluorescent coating, it is evident that the luminous eillciency of thelamp will be increased, at least as far as light emission in a aboutloss of efficiency. for reasons which have previously been mentioned.The possibility, thus secured, of using a relatively thick coating ofphosphor leads to ease in manufacture, since such coating may be appliedwith a considerable factor of safety above the minimum thicknessrequired to cover the strip.

Measurements made upon a fluorescent type tube employing a reflectingstrip covering approximately 180 degrees, and covered with a phosphor,showed a luminous output, over ap-- proximately 180 degrees, of 33 unitsin comparison with 23 units from a similar tube, drawing the same amountof electrical energy, but employing a phosphordistributed over theentire inner surface .ofthe tube, according to the hitherto prevailingpractice in the art.

In many cases, and particularly in the case of the form of strip of Fig.2B, it is preferred that an insulating coating cover the rear of thereflector strip also. The rear side of the strip may be coated with aless permeable or impervious insulation, such asporcelain enamel, inorder to minimize unwanted discharge on this side of the strip.

It will be evident that for ease in replacement,

, it will be desirable that the reflector strip be placed within thetube at a predetermined angular relationship to the 'contact-making pinsusually provided in pairs. at both ends of the tube. This will ensurethat, when a fixture or other device mounting the two sockets in whichthe tube is to v ylight source and the eye will be needed because of theopaque strip in the lamp. In either case, the strip serves as areflecting surface or secondary light source which cannot be reached bydust and dirt.

Referring now to Fig. 3. there is here shown a bulb In. provided at oneend with a conventional type of screw base. The electrodes il and l2pass through the press Il and connect to the terminals of the base. Apartition or strip Il extends from the press upwardly to a point nearthe other end of the bulb. 'I'his partition is shaped and sized to meetthe internal walls of the "bulb, s'o that the bulb is divided into twodiscrete compartments, open to one another only at the upper end of thebulb, and may be formed either of metal. as shown, or of insulatingreilective materials. 'I'he sides of this strip, if

formed of conductive material, are preferably coated with a suitablereilective and insulating material 4, such as previously described, sothat the latter will tend to minimize unwanted current ilow through thestrip.

The discharge extends upwardly in one chamber, crosses the upper end ofthe bulb, and descends in the other chamber. f i

In Fig. 4 there is shown a tube of the same general type as that shownin Fig. 1, the strip preferably being formed as shown in Fig. 2A or 2B.In this case the reflector strip is divided, at or near the center, sothat there are really two strips, discrete from one another, andoperating eiectively in series with one another. The general method ofoperation of this bulb is similar to that already described inconnection with Fig, 1. However, the two reflector strips, 31 and 32,present, together with the two electrodes, a total of three gaps, overwhich the cathode glow discharge must be initiated, before anyappreciable current will ilow through the reector system.

With the multiple reector strip employed in this particular form ofstructure of this invention, the total voltage drop across the gaps ofthe reflector strips and electrodes will be raised to a point where thepositive column will present less resistance to the current dischargethan will the reflector system. In this form, bare metallic surfaces maybe used, as there is no need for any insulating coating to preventundesired current now through the multiple reflector strip.

Among the novel advantages of that form of this invention which embodiesa separable strip is the fact that the actual application of theinsulating or fluorescent material does not have to take place withinthe relatively narrow confines of the glass tube. The strip ispreferably coated before insertion in the tube, thus making possiblecoating methods not so readily applicable to coating the inside of glasstubes. 'I'hese methods permit the use of iiuorescent powder or piguments which do not have to be subjected to the prolonged grinding orball-milling now customary in making suspensions for coating the innersur- 'faces of iluorescent lamps.

The less the grinding of the fluorescent particles, the more eiiicientthey are. Likewise, less care will be needed in applying this coatingthan is needed in applying it to an ordinary fluorescent lamp, sinceexcess thickness upon any portion of the strip will not give rise touneven illumination of the bulb. I have found that coatings made fromthe usual iluorescent silicates may be as much as several thousandths ofan inch in thickness.

It is often 'advantageous to combine in one element a reflector and astarting strip. This embodiment o! my invention is described in theabove-identiiled co-pending application.

While there have been described certain nonlimlting forms o! thisinvention, other forms will be apparent to those skilled in the art, andthe charge within said envelope, a plurality of metallic reilectorsinsulated from one another and substantially coextensive with the pathof said discharge and means for substantially preventing discharge viasaid reflectors, said discharge preventing means including the pluralityof insulating gaps separating said reflectorsinto electrically discretesections and presenting a total series cathode fall of potential inexcess of the potential required for establishing said positive columndischarge co-extensively with said reiiectols.

2. A device according to claim 1, also including a coating of discretenon-conductive particles substantially completely covering theilluminated surfaces of said reflectors.

3. A device according to claim 2, in which said coating is formed of aiiuorescert material.

4. In a gas discharge lamp, a gas-containing tube, a reflector situatedlongitudinally along a substantial portion of the path of gas dischargeand comprising a plurality of metallic reilective elements, electricallyseparated from one another and from the tube electrodes and sufficientin number so that the total cathode fall of potential required toestablish a discharge via said series of reflective elements exceeds thepotential established along said portion of said gas discharge path,whereby electrical discharges via said reflector are prevented, saidreflective elements being made of resilient metal strips,`each having anormal width greater than the internal diameter 4 of Asaid tube, eachelement being deformed from a single plane, whereby the expansivetendency of the elements retains said elements in position within saidtube.

MILES PENNYBACKER.

REFERENCES CITED The following references are of record in the Ville ofthis patent:

UNITED STATES PATENTS

